Textured balloons

ABSTRACT

A cutting balloon for use in PTCA and PTA procedures and methods for manufacturing cutting balloons are disclosed. One or more surfaces of the cutting balloon are formed with a non-smooth surface texture to improve adhesion between cutting blades and the inflatable balloon, to improve traction between the cutting balloon and the arterial wall, or to prevent inadvertent balloon perforation by a cutting blade. Textures, which can include a knurling texture and a nodular texture can be formed on the inflatable balloon surface directly using laser ablation. Alternatively, the texture can be formed on a mold surface used to mold the inflatable balloon from a parison. Mold surfaces can be textured using a laser photolithography process, sandblasting or a high-speed tool such as a diamond saw.

FIELD OF THE INVENTION

The present invention pertains generally to medical devices. Moreparticularly, the present invention pertains to balloon catheters. Thepresent invention is particularly, but not exclusively, useful as acutting balloon for the revascularization of coronary and peripheralvessels.

BACKGROUND OF THE INVENTION

Although conventional percutaneous, transluminal, coronary angioplasty(PTCA) and percutaneous, transluminal, angioplasty (PTA) procedures havebeen somewhat effective in treating coronary artery disease, incisingdevices, such as cutting balloons, are currently viewed by many as thenext generation treatment option for the revascularization of bothcoronary and peripheral vessels. The cutting balloon mechanism is uniquein that the balloon pressure is distributed over one or more blades(i.e. microtomes). The blade(s) function as stress concentrators and cutinitiators in PTCA and PTA procedures. Importantly, PTCA and PTAprocedures that employ cutting balloons for this purpose have beenproven to minimize vessel recoil, lessen vessel injury and lower therate of restenosis, as compared to conventional PTCA and PTA procedures.

In the past, typical cutting balloons have been prepared by firstencapsulating a portion of an incising element, such as a metal cuttingblade, in a blade pad. The blade pad is then adhesively bonded to thesmooth outer surface of an inflatable balloon. In some instances,however, this type of bond between the blade pad and the balloon hasbeen somewhat inadequate due to the inability of the adhesive to bond tothe smooth surfaces of the balloon and pad. In particular, relativelylong blades require a strong bond due to the differential expansion rateof the metal blade and the flexible balloon material. An inadequate bondis especially troublesome in light of the grave consequences that canresult if a blade pad de-bonds from the balloon while the balloon islocated in a sensitive area of the patient. For example, a de-bonding ofa blade pad from an inflatable balloon in or near the heart would inmost cases require immediate, high-risk open-heart surgery to remedy.

The cutting blades used in cutting balloons are extremely sharp (e.g.three to five times sharper than a conventional scalpel). In the absenceof suitable precautions, the sharp blades can tear, cut or perforate thethin, fragile inflatable balloon during assembly of the cutting balloon,handling or during clinical use. In a worst case, a balloon perforationor tear can result in an unsuccessful PTCA/PTA procedure and the loss ofinflation fluid into the patient's vasculature.

In a typical PTCA and PTA procedure, a cutting balloon is advancedthrough the vasculature of a patient with the balloon in a deflatedconfiguration. The balloon is then precisely positioned across a lesionin the vessel that is to be treated. Once the balloon has been properlypositioned, fluid is infused into the balloon to expand the balloon intoan inflated configuration. As the balloon expands, the blades cut intothe lesion and the surface of the balloon presses against the lesion,dilating the lesion to increase the effective diameter of the vessel. Inturn, the portion of the lesion that is in contact with the balloonproduces reactive forces on the balloon. For a lesion that islubricious, the reactive forces may overcome the frictional forcesbetween the balloon and the lesion. If this happens, slippage can occurbetween the balloon and the lesion resulting in unwanted movement of theballoon relative to the lesion. For instance, the reactive forces cancause the balloon to shoot forward or backward through the vessel in alongitudinal direction (i.e., “the watermelon seed effect”). Thisunwanted movement is often deleterious to the PTCA and PTA procedurebecause dilation and cutting may not occur at the desired location inthe vessel. Thus, unless unwanted movement of the balloon relative tothe lesion can be prevented, the effectiveness of the PTCA and PTAprocedure may be significantly reduced.

In light of the above, it is an object of the present invention toprovide cutting balloons and methods for their manufacture havingcutting blades that are strongly bonded to the surface of an inflatableballoon. It is another object of the present invention to providemethods for forming surface textures on one or more cutting balloonsurfaces to promote adhesion between the cutting blades and theinflatable balloon, to improve traction between the cutting balloon andthe arterial wall, or to prevent inflatable balloon perforation by acutting blade. Yet another object of the present invention is to providecutting balloons and methods for their manufacture that are easy to use,relatively simple to implement, and comparatively cost effective.

SUMMARY OF THE INVENTION

The present invention is directed to incising devices, such as cuttingballoons, for use in vessel revascularization and methods formanufacturing incising devices. A typical incising device includes aninflatable balloon, one or more elongated incising elements, and one ormore mounting pads (e.g. blade pads). For the present invention, theincising elements can include, but are not limited to, cutting blades,round wires and hardened polymers. Each mounting pad is bonded to theinflatable balloon and is provided to hold a respective incisingelement. For the present invention, one or more surfaces of the incisingdevice are formed with a non-smooth surface texture to enhance theperformance of the incising device. The non-smooth surface texture caninclude, but is not limited to, a knurling texture, a nodular texture,or a texture having spiral, sinuous or random indentations.

In a first aspect of the present invention, a portion of the outersurface of the inflatable balloon is formed with non-smooth surfacetexture such as a knurling texture. A mounting pad is then adhesivelybonded to the textured surface of the inflatable balloon. The texturedsurface provides more surface area than a similarly sized smoothsurface, and accordingly, a stronger bond is obtained between theinflatable balloon and the mounting pad. Alternatively, or in additionto forming a portion of the inflatable balloon with a non-smooth surfacetexture, a bonding surface on the mounting pad can be formed with anon-smooth surface texture to increase the bond strength between theinflatable balloon and the mounting pad.

In another aspect of the present invention, non-bonding surfaces of theinflatable balloon (i.e. surfaces that remain exposed after the mountingpad(s) have been bonded to the inflatable balloon) are formed with anon-smooth surface texture. In one embodiment, the exposed surface ofthe inflatable balloon is formed with a plurality of nodules thatprevent the incising elements from puncturing the inflatable balloon. Inanother embodiment, an exposed portion of the working section of theinflatable balloon is textured to promote traction between theinflatable balloon surface and the affected arterial wall to anchor theincising device at the treatment site during a balloon inflation. Otherapplications for the texture include balloon identification and the useof a spiral pattern in stripped balloons to increase flexibility with aminimal effect on burst pressure.

In another aspect of the invention, a method for manufacturing anincising device includes the step of providing an inflatable balloonhaving an inner surface for surrounding an inflation volume and anopposed outer surface having at least one surface portion formed with anon-smooth surface texture. The method further includes the step ofmounting at least one incising element on the outer surface of theinflatable balloon.

In a first embodiment of the manufacturing method, the step of providingan inflatable balloon having at least one surface portion formed with anon-smooth surface texture is accomplished by providing a mold having asmooth mold surface and forming a non-smooth surface texture on at leasta portion of the mold surface. A parison is then positioned in the moldand expanded onto the mold surface to produce the inflatable balloonhaving the non-smooth surface texture. The non-smooth surface texturecan be formed on the mold surface using one of several procedures. In afirst procedure, a non-smooth surface texture is formed on the moldsurface using a laser photolithography procedure. Alternatively, anon-smooth surface texture can be formed on the mold surface byselectively sandblasting portions of said mold surface or the texturecan be formed using a diamond saw.

In another embodiment of the manufacturing method, the step of providingan inflatable balloon having at least one surface portion formed with anon-smooth surface texture is accomplished by providing an inflatableballoon having a smooth outer surface. Next, a laser is used to ablatethe smooth outer surface of the balloon to form the non-smooth surfacetexture.

To mount an incising element on the outer surface of the inflatableballoon, the manufacturing method may include the steps of encapsulatinga portion of the incising element in a mounting pad and adhesivelybonding the mounting pad to the surface portion of the inflatableballoon formed with a non-smooth surface texture. In one implementation,the mounting pad is first formed with a smooth bonding surface. Next, alaser is used to ablate the bonding surface to form a non-smooth surfacetexture thereon. The textured bonding surface is then adhesively bondedto the surface portion of the inflatable balloon that is formed with anon-smooth surface texture.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of this invention, as well as the invention itself,both as to its structure and its operation, will be best understood fromthe accompanying drawings, taken in conjunction with the accompanyingdescription, in which similar reference characters refer to similarparts, and in which:

FIG. 1 is a simplified, perspective view of a catheter having a cuttingballoon operationally positioned in the upper body of a patient;

FIG. 2 is an enlarged, perspective view of a cutting balloon;

FIG. 3 is a cross-sectional view of the cutting balloon shown in FIG. 2as seen along line 3-3 in FIG. 2;

FIG. 4 is a simplified, perspective view of a blade encapsulated in ablade pad;

FIG. 5 is a simplified schematic view of a laser source ablating thesurface of an inflatable balloon to form a non-smooth surface texturethereon;

FIG. 6 is a representative illustration of a surface having a knurledsurface texture formed thereon;

FIG. 7 is a representative illustration of a surface having a nodularsurface texture formed thereon;

FIG. 8 is a is a simplified schematic view of a laser source activatinga photoresist on the surface of a mold to form a non-smooth surfacetexture thereon;

FIG. 9 is a simplified schematic view of a parison positioned forexpansion in a mold having a non-smooth surface texture formed thereon;and

FIG. 10 is an enlarged view of a cutting balloon positioned at atreatment site.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to FIG. 1, a catheter 20 having an incising device,which in this case is a cutting balloon 22, is shown for performing amedical procedure at an internal treatment site of a patient 24. Morespecifically, the catheter 20 is shown positioned to treat a lesion inan upper body artery. Although the catheter 20 is capable of performinga medical procedure in an upper body artery such as a coronary artery,those skilled in the pertinent art will recognize that the use of thecatheter 20 as herein described is not limited to use in a specificartery, but, instead can be used in vascular conduits and other ductalsystems throughout the human body.

Referring now to FIG. 2, the distal portion of the catheter 20 is shownto include a cutting balloon 22 that is attached to the distal end 26 ofan inflation tube 28. FIG. 2 further shows that the cutting balloon 22can include an inflatable balloon 30 that typically includes acylindrical shaped working section 32 that defines an axis 33.Typically, the inflatable balloon 30 is made of a relatively flexiblepolymeric material such as, but not limited to, polyethyleneterephthalate (PET). As best seen in FIG. 3, the inflatable balloon 30can be characterized as having an outer surface 34 and an opposed innersurface 36 that surrounds an inflation volume 38, which in turn, can beinfused with a medical grade fluid to expand the inflatable balloon 30.More specifically, as shown in FIG. 1, a fluid pump 40 can be activatedto pump a medical grade fluid from a fluid reservoir 42 and through theinflation tube 28 to expand the inflatable balloon 30.

Cross-referencing FIGS. 2 and 3, it can be seen that the cutting balloon22 further includes a plurality of elongated incising elements, whichfor the embodiment shown are cutting blades 44. In alternateembodiments, round wires or hardened polymers are used as incisingelements. For the embodiment shown, four longitudinally aligned blades44 are uniformly distributed around the circumference of the workingsection 32 of the inflatable balloon 30. Typically, each blade 44 ismade of a medical grade metal such as stainless steel. As best seen inFIG. 3, a portion of each blade 44 is encapsulated in a respective bladepad 46, thereby affixing the blade 44 to the respective blade pad 46.Typically, each blade pad 46 is made of a relatively flexible polymericmaterial such as polyurethane. From the blade pad 46, each blade 44extends radially to a sharp edge 48. Cross-referencing FIGS. 3 and 4, itcan be seen that each blade pad 46 includes a bonding surface 50 that isadhesively bonded to a bonding surface 52 on the outer surface 34 of theinflatable balloon 30 using an adhesive such as polyurethane.

In a first embodiment of the catheter 20, one or both of the bondingsurfaces 50, 52 are formed with a non-smooth surface texture to increasethe strength of the adhesive bond between the blade pad 46 and the outersurface 34 of the inflatable balloon 30. FIG. 5 illustrates a firstmanufacturing method for forming a non-smooth surface texture on abonding surface 50, 52, which in this case is a longitudinally alignedstrip located on the working section 32 of the inflatable balloon 30.FIG. 5 illustrates that a laser source 54 can be used to ablate balloonmaterial on the outer surface 34 of the inflatable balloon 30. The lasersource 54 can also be used to ablate blade pad material on the bondingsurface 50 of a blade pad 46.

The laser source 54 may include a direct writing KrF excimer laseroperating at 248 nm or a HeCd laser operating at 442 nm, that generatesa laser beam. In addition, the laser source 54 may include optics toboth focus the beam on the outer surface 34 and scan the beam along theouter surface 34 of the inflatable balloon 30. Using this technique, aknurling texture as shown in FIG. 6 can be produced on the curved outersurface 34 having a first set of parallel grooves and a second set ofparallel grooves that are aligned at an angle relative to the first setof grooves. Grooves having an approximate width in the range of 5-10 μmcan be used to increase the effective surface area of the bondingsurface by approximately 50-100%. In some cases, a stencil, mask orphoto-resist material can be used to limit the ablation to selectedareas on the outer surface 34.

The laser source 54 can be used to ablate portions (or all) of the outersurface 34 with a nodule texture, such as the texture shown in FIG. 7,to improve traction between the cutting balloon 22 and the arterialwall, or to prevent perforation of the inflatable balloon 30 by acutting blade 44 during assembly, handling or clinical use.

FIG. 8 illustrates an alternative manufacturing method for forming anon-smooth surface texture on the outer surface 34 of the inflatableballoon 30. In this manufacturing method, laser photolithography isfirst used to form a texture, such as the knurling texture shown in FIG.6, on the initially smooth surface 56 of a mold half 58 a. Thistechnique is similar to the technique used in the fabrication ofintegrated circuits. A photomask is placed on the surface 56 and laserlight from laser source 54 is used to selectly activate the photoresistto create the desired texture. The laser source 54 may include a directwriting KrF excimer laser operating at 248 nm or a HeCd laser operatingat 442 nm, that generates a laser beam. In addition, the laser source 54may include optics to both focus the beam on the surface 56 and scan thebeam along the surface 56 of the mold half 58 a. Where laser lightstrikes the photoresistive material, its composition is changed.Photoresistive material not affected by light is washed off. Finally,the surface 56 is exposed to an etching solution such as potassiumhydroxide that dissolves portions of the surface 56 not protected by thephotoresistive material to create the desired texture pattern on thesurface 56 of the mold half 58 a. Alternatively, a non-smooth surfacetexture can be formed on the mold surface 56 by selectively sandblastingportions of said mold surface 56 or the texture can be formed using ahigh speed tool such as a diamond saw.

As shown in FIG. 9, once the desired texture pattern has been formed onthe surface 56 of the mold half 58 a, a parison, which in this case is ahollow tube 60 made of a polymeric material such as polyethyleneterephthalate (PET), is heated to a working temperature and placed inthe cavity of the two-piece mold 58 a,b. With the tube 60 positioned inthe mold cavity and the mold 58 a,b closed, the lumen 62 of the tube 60is pressurized to radially expand the tube 60 onto the mold surface 56.It is to be appreciated that the mold half 58 a will transfer (e.g.stamp) the non-smooth surface texture onto portions of the tube 60. Theresult is an inflatable balloon 30 having a non-smooth surface textureon selected portions (or all) of its outer surface 34. Using this moldtransfer technique, a knurling texture as shown in FIG. 6 can beproduced on the curved outer surface 34 having a first set of parallelgrooves and a second set of parallel grooves that are aligned at anangle relative to the first set of grooves. Grooves having anapproximate width in the range of 5-10 μm can be used to increase theeffective surface area of the bonding surface by approximately 50-100%.

The laser source 54 shown in FIG. 8 can be used to form a nodule textureon the surface 56 of the mold half 58 a, such as the texture shown inFIG. 7. The nodular texture is then transferred to the outer surface 34of the inflatable balloon 30 during radial expansion of a parison, asdescribed above. The nodular texture can be used to improve tractionbetween the cutting balloon 22 and the arterial wall, or to preventperforation of the inflatable balloon 30 by a cutting blade 44 duringassembly, handling or clinical use.

A typical use of the catheter 20 can best be appreciated withcross-reference to FIGS. 1 and 10. In a typical use, the cutting balloon22 is deflated and inserted into the vasculature of the patient 24 usinga peripheral artery, such as the femoral artery, for access. Once in thevasculature, the cutting balloon 22 is advanced to a treatment site suchas the treatment site shown in FIG. 10, which illustrates a coronaryartery 64 that is constricted by a lesion 66. With the working sectionof the balloon 32 positioned across to the lesion 66, the fluid pump 40is activated to pass a fluid through the inflation tube 28 and into theinflatable balloon 30. As the inflatable balloon 30 expands, one or moreof the blades 44 contact the lesion 66 and function as stressconcentrators and cut initiators. In addition, a non-smooth surfacetexture on the outer surface 34 of the inflatable balloon 30 engages thelesion 66, anchoring the cutting balloon 22 at the treatment site,preventing longitudinal movement of the balloon 30 during furtherinflation of the inflatable balloon 30. Thus, the inflatable balloon 30can be further inflated without longitudinal balloon movement allowingthe cutting balloon 22 to cut and compact the lesion 66 and dilateartery 64.

While the particular textured balloons and methods of manufacture asherein shown and disclosed in detail are fully capable of obtaining theobjects and providing the advantages herein before stated, it is to beunderstood that they are merely illustrative of the presently preferredembodiments of the invention and that no limitations are intended to thedetails of construction or design herein shown other than as describedin the appended claims.

1. An incising device comprising: an inflatable balloon having an innersurface for surrounding an inflation volume and an opposed outersurface, said outer surface having at least one surface portion formedwith a non-smooth surface texture; and at least one incising elementmounted on said outer surface of said balloon.
 2. An incising device asrecited in claim 1 wherein said incising element is a cutting blade. 3.An incising device as recited in claim 2 wherein said cutting blade ispartially encapsulated in a blade pad and said blade pad is adhesivelybonded to said textured portion of said balloon.
 4. An incising deviceas recited in claim 3 wherein said blade pad includes a bonding surfaceformed with a non-smooth texture and said bonding surface is adhesivelybonded to said textured portion of said balloon.
 5. An incising deviceas recited in claim 3 wherein said non-smooth texture is a knurlingtexture.
 6. An incising device as recited in claim 3 wherein saidknurling texture comprises a plurality of grooves having a groove widthbetween approximately five microns (5 μm) and approximately ten microns(10 μm).
 7. An incising device as recited in claim 2 wherein saidnon-smooth texture comprises a plurality of nodules formed on said outersurface to prevent said blades from perforating said balloon.
 8. Amethod for manufacturing an incising device, said method comprising thesteps of: providing an inflatable balloon having an inner surface forsurrounding an inflation volume and an opposed outer surface, said outersurface having at least one surface portion formed with a non-smoothsurface texture; and mounting at least one incising element on saidouter surface of said balloon.
 9. A method as recited in claim 8 whereinsaid step of providing an inflatable balloon is accomplished by:providing a parison; providing a mold having a smooth mold surfaceportion; forming a non-smooth surface texture on said smooth moldsurface portion; and expanding said parison onto said mold surface. 10.A method as recited in claim 9 wherein said step of forming a non-smoothsurface texture on said mold surface is accomplished by: coating atleast a portion of said mold surface with photoresist; exposing selectedportions of said photoresist using laser light; developing saidphotoresist; and etching the mold surface.
 11. A method as recited inclaim 9 wherein said step of forming a non-smooth surface texture onsaid mold surface is accomplished by selectively sandblasting portionsof said mold surface.
 12. A method as recited in claim 9 wherein saidstep of forming a non-smooth surface texture on said mold surface isaccomplished using a diamond saw.
 13. A method as recited in claim 8wherein said step of providing an inflatable balloon is accomplished by:providing an inflatable balloon having a smooth outer surface; and laserablating said smooth outer surface to form said non-smooth surfacetexture on said at least one portion of said outer surface.
 14. A methodas recited in claim 8 wherein said incising element is a cutting bladeand said step of mounting at least one incising element on said outersurface of said balloon is accomplished by: encapsulating a portion ofsaid cutting blade in a blade pad; and adhesively bonding said blade padto said surface portion formed with a non-smooth surface texture.
 15. Amethod as recited in claim 8 wherein said incising element is a cuttingblade and said step of mounting at least one incising element on saidouter surface of said balloon is accomplished by: encapsulating aportion of said cutting blade in a blade pad, said blade pad formed witha smooth bonding surface; laser ablating said smooth bonding surface toform said non-smooth surface texture on said bonding surface; andadhesively bonding said bonding surface of said blade pad to saidsurface portion of said balloon formed with a non-smooth surfacetexture.
 16. A cutting balloon comprising: a cutting blade; a blade padfor holding said cutting blade, said blade pad formed with a bondingsurface; an inflatable balloon having an inner surface for surroundingan inflation volume and an opposed outer surface, said outer surfaceformed with a bonding surface, wherein at least one of said blade padbonding surface and said balloon bonding surface are formed with anon-smooth surface texture to increase the surface area of said bondingsurface; and an adhesive for bonding said blade pad bonding surface andsaid balloon bonding surface.
 17. A cutting balloon as recited in claim16 wherein said blade pad bonding surface is formed with a non-smoothsurface texture.
 18. A cutting balloon as recited in claim 16 whereinsaid balloon bonding surface is formed with a non-smooth surfacetexture.
 19. A cutting balloon as recited in claim 16 wherein said bladepad bonding surface and said balloon bonding surface are formed with anon-smooth surface texture.
 20. A cutting balloon as recited in claim 16wherein said non-smooth texture is a knurling texture.